Removal of phenolic compounds from a petrochemical effluent with a methanogenic consortium

A methanogenic consortium was used to degrade phenol and ortho- (o-) cresol from a specific effluent of a petrochemical refinery. This effluent did no t meet the local environmental regulations for phenolic compounds (178 mg/L ), oils and greases (61 mg/L), ammoniacal nitrogen (75 mg/L) or sulfides (3 .2 mg/L). The consortium, which degrades phenol via its carboxylation to be nzoic acid, was progressively adapted to the effluent. Despite the very hig h effluent toxicity (EC50 of 2% With Microtox), the adapted consortium degr aded 97% of 156 mg/L phenol in the supplemented effluent after 13 days in b atch cultures (serum bottle). The addition of proteose peptone to the efflu ent is essential for phenol degradation. o-cresol was also transformed but not meta- or para-cresols. A continuous flow fixed-film anaerobic bioreacto r was developed with the consortium. Treating the effluent with the bioreac tor reduced phenol and phenolic compounds concentrations by 97 and 83%, res pectively, for a hydraulic residence time of 6 h. This treatment also reduc ed by about half the effluent toxicity. Oils and greases and ammoniacal nit rogen were not affected. Similar microbiological forms were observed in ser um bottles and in the bioreactors with or without the petrochemical effluen t. These results indicate that this methanogenic consortium can treat effic iently the phenolic compounds in this specific petrochemical effluent.